a, ĐKXĐ \(\left\{{}\begin{matrix}x\ne1\\x\ne-1\end{matrix}\right.\)
b,Ta có: \(B=\left(\dfrac{x+1}{2x-2}+\dfrac{3}{x^2-1}-\dfrac{x+3}{2x+2}\right).\dfrac{4x^2-4}{5}\)
\(=\left[\dfrac{\left(x+1\right)^2}{2\left(x-1\right)\left(x+1\right)}+\dfrac{6}{2\left(x-1\right)\left(x+1\right)}-\dfrac{\left(x+3\right)\left(x-1\right)}{2\left(x+1\right)\left(x-1\right)}\right].\dfrac{4\left(x-1\right)\left(x+1\right)}{5}\)
\(=\dfrac{x^2+2x+1+6-\left(x^2+2x-3\right)}{2\left(x-1\right)\left(x+1\right)}.\dfrac{4\left(x-1\right)\left(x+1\right)}{5}\)
\(=\dfrac{2.10}{5}=4\)
Vậy giá trị của B ko phụ thuộc vào giá trị của biến x
